Radiography: vascular contrast studies

• Injection of positive contrast into circulation allows visualization of vascular system.

• Investigation of:
  • Cardiac chamber size.
  • Cardiac wall thickness.
  • Position of blood vessels.
  • Suspected shunts in heart Patent ductus arteriosus , liver Congenital portosystemic shunt (CPSS) or circulation.
  • Thromboembolic disease, aortic or pulmonary.
• Assessment of perfusion.

Advantages

• Relatively simple procedure.
• Equipment available in general practice.
• Good anatomical detail.

Disadvantages

• General anesthesia often required (and patient may be severely compromised).
• Fluoroscopy required for selective angiography.

• Scintigraphy (allows assessment of vascular perfusion and ventilation perfusion ratio).
• Ultrasonography for measurement of cardiac chamber size, presence of vascular shunts and thrombotic disease.
• Fluoroscopy gives better visualization of dynamic lesions.

Preparation

• 15 min.

Procedure

• 10 min.

Criteria for choosing test

• Is the examination appropriate?
• Can you make the diagnosis without it?
• Will your management of the case be affected by the outcome of the examination?

Risk assessment

• For many conditions where vascular contrast studies are indicated the patient is likely to be clinically ill, eg pulmonary thromboembolism, therefore careful assessment of risks of anesthesia/sedation should be made.

Minimum equipment

• X-ray machine that allows rapid multiple exposures to be made.
• Cassette.
• Processing facilities.
• Protective clothing (lead apron) for radiographer.
• Positioning aids (sandbags, cradle and ties).
• Method of labelling film.
• Cassette tunnel.

Ideal equipment

• Rapid cassette changer to allow multiple exposures to be made.
• Ability to process films during procedure so that repeat radiographs can be taken during course of study if required.
• High output X-ray machine.
• High definition screen.
• Grid for examination of large dog.

Minimum consumables

• Radiographic film.
• Intravenous catheter (large bore; 20G).
• Contrast agent (water-soluble, iodine-based).

Ideal consumables

• Ideally non-ionic, low osmolar water-soluble contrast is used, eg iohexol as this is less likely to cause circulatory disturbances.

• General anesthesia.

• Pre-place catheter in peripheral vein (for non-selective angiography), usually jugular or cephalic Cephalic catheterization.
• Catheterization of specific region requires more experience and may need fluoroscopic guidance.

Step 1 - Control Films

• Check exposure settings and processing.
• Confirm positioning adequate.
• Confirm diagnosis not apparent without contrast study.

Step 1 - Non-selective angiography

• Inject contrast agent 200 mg iodine/0.45 kg as rapidly as possible.
  In large dogs injection via the jugular is preferable to permit rapid infusion of large volumes required.

Step 2 - Selective angiography

• Introduce bolus of contrast agent at specific site, eg cardiac chamber, renal artery.
  Fluoroscopy may be required to ensure catheter in correct site at time of injection.

Step 3 - Make exposure

• Make exposure immediately after injection.
• Exposure multiple films in rapid succession.

Step 1 - Assess radiographs

• Has structure of interest been exposed during time of contrast presence?
• If not, repeat films after second contrast injection.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Wise M (1982) Non-selective angiocardiography in the normal dog and cat. Vet Radiol 23 (4), 144-151 VetMedResource.

Other sources of information

• Fox P R & Bond B R (1983) Non-selective and selective​ angiocardiography. Vet Clin North Am Small Anim Pract 13 (2), 259-272 PubMed.